Android Studio使用Gradle构建系统，能过简化编译、打包、测试过程； Gradle构建配置文件有3个Gradle的主要配置文件，为项目或模块的构建进行配置，分别是：setting.gradle、顶级配置文件（根目录下build.gradle）、模块配置文件（模块目录下的build.gradle），还有2个是配置Gradle的属性文件为gradle.properties和local.properties；

1.Gradle属性文件

1.1 gradle.properties

gradle.properties位于项目根目录下，主要设置Gradle后台进程JVM内存大小、日记级别等等；

Gradle属性配置参考：Gradle属性配置

1.2 local.properties

为Gradle配置环境变量，例如sdk、ndk路径；

2. setting.gradle

此配置文件位于根目录下，用于指示Gradle在构建应用时应将哪些模块包含在内；

多个模块之间用空格隔开

include ':app', ':lib'

3.顶级配置文件

此配置文件位于项目根目录下，用于定义项目所有模块的配置文件，

/**
 * The buildscript {} block is where you configure the repositories and
 * dependencies for Gradle itself--meaning, you should not include dependencies
 * for your modules here. For example, this block includes the Android plugin for
 * Gradle as a dependency because it provides the additional instructions Gradle
 * needs to build Android app modules.
 */

buildscript {

    /**
     * The repositories {} block configures the repositories Gradle uses to
     * search or download the dependencies. Gradle pre-configures support for remote
     * repositories such as JCenter, Maven Central, and Ivy. You can also use local
     * repositories or define your own remote repositories. The code below defines
     * JCenter as the repository Gradle should use to look for its dependencies.
     */

    repositories {
        google()
        jcenter()
    }

    /**
     * The dependencies {} block configures the dependencies Gradle needs to use
     * to build your project. The following line adds Android Plugin for Gradle
     * version 3.1.0 as a classpath dependency.
     */

    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.0'
    }
}

/**
 * The allprojects {} block is where you configure the repositories and
 * dependencies used by all modules in your project, such as third-party plugins
 * or libraries. Dependencies that are not required by all the modules in the
 * project should be configured in module-level build.gradle files. For new
 * projects, Android Studio configures JCenter as the default repository, but it
 * does not configure any dependencies.
 */

allprojects {
   repositories {
       google()
       jcenter()
   }
}

3.1 buildscript{ }

主要配置Gradle代码托管库和依赖项；

3.1.1 repositories{ }

Gradle引用代码托管库，Gradle预先配置了远程支持JCenter、Maven、Central和lvy等存储区，当然也可以指定本地自定义的远程存储库,eg:google()；

JCenter():就可以使用JCenJCenter上托管的开源项目；

1.2 dependencies{ }

项目依赖Gradle的插件版本路径；

3.2 allprojects{ }

配置所有模块中使用的依赖项，例如第三方插件或libraries；

4. 模块配置文件

参考：模块配置文件-build.gradle

5. Gradle-Wrapper配置

参考：Gradle-Wrapper详解

Gradle配置文件详解